Zhong Chen

Bio: Zhong Chen is an academic researcher from Nanyang Technological University. The author has contributed to research in topics: Medicine & Chemistry. The author has an hindex of 80, co-authored 1000 publications receiving 28171 citations. Previous affiliations of Zhong Chen include Institute of High Performance Computing Singapore & National Institute of Education.

Origins of Inhomogeneous Light Emission From GaN-Based Flip-Chip Green Micro-LEDs

Abstract: Spatially resolved electroluminescence emitted through the sapphire substrate of GaN-based flip-chip green microscale light-emitting diodes with $20\times 20\,\,\mu \text{m}^{\text {2}}$ mesas has been collected via microscopic hyperspectral imaging. The current crowding is identified in the central region of the mesa, corresponding to the position of the p-pad. The bright-spot emissions at the edges of the mesa originate from localized potential energy valleys. This letter suggests that the comprehensive information about current crowding and the distribution of the light emission across the mesa of microscale light-emitting diode can be obtained by capturing spatially resolved light emission from the side of the transparent substrate.

Remarkable Black-Phase Robustness of CsPbI3 Nanocrystals Sealed in Solid SiO2 /AlOx Sub-Micron Particles.

Abstract: This work combines the high-temperature sintering method and atomic layer deposition (ALD) technique, and yields SiO2 /AlOx -sealed γ-CsPbI3 nanocrystals (NCs). The black-phase CsPbI3 NCs, scattered and encapsulated firmly in solid SiO2 sub-micron particles, maintain in black phases against water soaking, ultraviolet irradiation, and heating, exhibiting remarkable phase stability. A new phase-transition route, from γ via β to α phase without transferring into δ phase, has been discovered upon temperature increasing. The phase stability is ascribed to the high pressure exerted by the rigid SiO2 encapsulations, and its condensed amorphous structures that prevent the permeation of H2 O molecules. Nanoscale coating of Al2 O3 thin films, which are deposited on the surface of the CsPbI3 -SiO2 by ALD, enhances the protection against O2 infiltration, greatly elevating the high-temperature stability of CsPbI3 NCs sealed inside, as the samples remain bright after 1-h annealing in air at 400 °C. These fabrication and encapsulation techniques effectively prevent the formation of δ-CsPbI3 under harsh environment, bringing the high-pressure preservation of black-phase CsPbI3 from laboratory to industry toward potential applications in both photovoltaic and fluorescent areas.

Improvements of mesopic luminance for light-emitting-diode-based outdoor light sources via tuning scotopic/photopic ratios.

Abstract: Outdoor light sources must guarantee excellent mesopic luminance (Lmes) for traffic safety at night. Here, we propose a solution to improve mesopic-related parameters, which include especially the scotopic/photopic ratio and the Lmes, of multi-chip light-emitting diode (LED) light sources. Generally, these sources are driven by pulse-width-modulation currents, and possess readily-controlled spectral power distributions (SPDs). An updated version of the optical power ratio algorithm developed in this article can select suitable overall SPDs and yield corresponding duty cycles to drive individual chips at different correlated-color temperatures and operating temperatures. Its accuracy and practicality are proven by experimental results. In addition, our study introduces a temperature-feedback technique that can instantly adjust duty cycles for each chip according to real-time operating temperatures in order to avoid undesirable color drifts at different operating temperatures. It can also be regarded as a model for practitioners who desire to improve the quality of outdoor light sources.

Cationic quaternary chalcohalide nanobelts: Hg4In2Q3Cl8 (Q = S, Se, Te)

Abstract: Novel cationic quaternary chalcohalide nanobelts were found in Hg4In2Q3Cl8 (Q = S, Se, Te), obtained by solid-state reaction. Due to the effects of dimensional reduction, both theoretical and experimental results demonstrate that their bandgaps are remarkably increased compared to those of the zinc-blende structure HgQ (Q = S, Se, Te).

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Principles of Neural Science

Abstract: I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Abstract: As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...